1. Field of the Invention
This invention relates to adhesive resins which have good adhesion to various other materials such as polyolefins, polyamides, polyesters, saponified ethylenevinyl acetate copolymers and metals, and also to laminates using the same. More particularly, the invention relates to adhesive resins which are obtained by chemically combining 0.01-10 parts by weight of ethylenically unsaturated fatty acids or derivatives thereof with 100 parts by weight of epoxy group-containing olefin polymers, and to laminates using such adhesive resins. The laminates are useful as food wrap films or materials for food containers.
2. Description of the Prior Art
There have heretofore been proposed and used various types of laminate products which are made by laminating such materials as polyolefins, polyamides, polyesters, saponified ethylene-vinyl acetate copolymers or metals with different kinds of materials so that one material compensates for the defect of another. For instance, laminates of polyolefins with polyamides or polyesters are known as food wrap materials. Because of their good transparency, flexibility, hygienic properties and heat sealability, polyolefins have been widely used as wrapping or packaging materials for foods. However, polyolefins have a shortcoming in that owing to their high permeability to gases such as oxygen, carbon dioxide and the like, they are unable to preserve foods over a long term. On the other hand, although polyamides have good resistance to heat and an oil, they are poor in vapor permeability and heat sealability. Polyesters or saponified ethylene-vinyl acetate copolymers have low gas permeability and good heat resistance, but they are disadvantageously poor in heat sealability. These disadvantages can be overcome by lamination of polyolefins and these other materials.
However, lamination of these materials involves the drawback that adhesion between these materials is poor, causing delamination or ply separation to readily occur.
There have been conventionally proposed, as adhesive resins capable of improving the interlaminar bond strength, ethylene-vinyl acetate copolymers, ionomer resins or polyolefin resins modified with maleic anhydride or the like (see, for example, Japanese Laid-open Patent Application Nos. 51-92880, 52-32080, 54-82, 54-87753 and 54-160481). However, these resins have good compatibility with polyolefins or polyamides and a fairly high interlaminar bond strength, but are not yet satisfactory. In addition, the strength of adhesion to polyesters is not so high as to stand practical use.